Southern Beardless-tyrannulet

The southern beardless tyrannulet is 10.2 cm (4.0 in) long, weighs 7.5 g (0.26 oz) and often resembles a tiny yellow-bellied elaenia. The head is dark brown or grey with an erectile crest and pale supercilium. The upperparts are grey-green becoming paler on the rump. The wings are brown with yellow feather-edging and two whitish, yellowish or cinnamon wing bars. The tail, which regularly is held cocked, is brown, the throat grey, the breast yellowish, and the abdomen yellow. The bill is black, but at least the base of the lower mandible is pale. Subspecies from humid regions (e.g. the Amazon basin) are generally greener with pure yellow bellies, while subspecies of drier regions (e.g. eastern Brazil and western Ecuador) generally are greyer with duller bellies. The subspecies C. o. venezuelae occurs only in Trinidad and Venezuela, and is well distinct in plumage tone. The call is a loud whistled TLEEE-tee-tee-tee. In courtship, the crests are raised, the tail flicked, and an excited mixture of the TLEE call and a churring pee-chrrr-pee-chrrr is given. Sexes are similar, and this species always appears brighter, especially with regard to the wing bars, than the closely related northern beardless tyrannulet (C. imberbe), with which it was once considered conspecific. However, the two forms overlap without interbreeding in central Costa Rica.